ENG-8050: background event updates set final=None

When `final=None`, the frontend does not update the `event_processing` flag.

Author: masenf

reflex/.templates/web/utils/state.js

@@ -665,7 +665,9 @@ export const connect = async (
       }
     }
     applyClientStorageDelta(client_storage, update.delta);
-    event_processing = !update.final;
+    if (update.final !== null) {
+      event_processing = !update.final;
+    }
     if (update.events) {
       queueEvents(update.events, socket, false, navigate, params);
     }

reflex/app.py

@@ -1556,11 +1556,14 @@ def all_routes(_request: Request) -> Response:
         )
 
     @contextlib.asynccontextmanager
-    async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
+    async def modify_state(
+        self, token: str, background: bool = False
+    ) -> AsyncIterator[BaseState]:
         """Modify the state out of band.
 
         Args:
             token: The token to modify the state for.
+            background: Whether the modification is happening in a background task.
 
         Yields:
             The state to modify.
@@ -1581,7 +1584,10 @@ async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
                 # When the state is modified reset dirty status and emit the delta to the frontend.
                 state._clean()
                 await self.event_namespace.emit_update(
-                    update=StateUpdate(delta=delta),
+                    update=StateUpdate(
+                        delta=delta,
+                        final=True if not background else None,
+                    ),
                     token=token,
                 )
 

reflex/istate/proxy.py

@@ -131,7 +131,9 @@ async def __aenter__(self) -> StateProxy:
 
         await self._self_actx_lock.acquire()
         self._self_actx_lock_holder = current_task
-        self._self_actx = self._self_app.modify_state(token=self._self_substate_token)
+        self._self_actx = self._self_app.modify_state(
+            token=self._self_substate_token, background=True
+        )
         mutable_state = await self._self_actx.__aenter__()
         super().__setattr__(
             "__wrapped__", mutable_state.get_substate(self._self_substate_path)

reflex/state.py

@@ -1779,7 +1779,7 @@ async def _as_state_update(
             return StateUpdate(
                 delta=delta,
                 events=fixed_events,
-                final=final if not handler.is_background else True,
+                final=final if not handler.is_background else None,
             )
         except Exception as ex:
             state._clean()
@@ -2684,7 +2684,7 @@ class StateUpdate:
     events: list[Event] = dataclasses.field(default_factory=list)
 
     # Whether this is the final state update for the event.
-    final: bool = True
+    final: bool | None = True
 
     def json(self) -> str:
         """Convert the state update to a JSON string.